In a conventional clinical study of an anticancer agent, its toxicity profile and maximum recommended dose are first determined in the Phase I clinical study, and then the agent is evaluated as a drug based on the response rate using the tumor reduction rate as a criterion for efficacy in the Phase II clinical study. Meanwhile, with the advancement in cancer biology in recent years, drugs having a novel action mechanism for inhibiting the intracellular signal transduction system, angiogenesis and so forth are in the course of active research and development. For these novel anticancer agents, it may be possible that a maximum recommended dose close to a toxic dose does not necessarily need to be administered. Further, it is estimated that drug efficacy could be more appropriately judged by using improvement of QOL (Quality of Life) or prolongation of life associated with tumor growth inhibition as an index rather than tumor reduction. In this case, to more logically and specifically confirm the drug efficacy, it is desirable to utilize change of a biological marker closely relating to a tumor growth inhibition mechanism as a surrogate marker.
In the anticancer therapy, in general, reactivity of a living body when an anticancer agent is administered is largely depends on susceptibility of a tumor cell, which is a target of the drug, to the drug. Generally, this susceptibility of tumor cell to the drug greatly varies in every type of tumor cell. Such differences in susceptibility are attributable to quantitative or qualitative differences of target molecules of the drug or factors relating to the molecules, acquisition of drug resistance and so forth. Considering such a background, it would be very useful if change in a tumor cell specifically caused when the tumor cell as a target exhibits susceptibility to a drug can be measured by using tumor tissue obtained by biopsy etc., because early determination of drug efficacy, establishment of a treatment method, selection of a new treatment method and so forth become possible by using the change as a surrogate marker. Further, if a tumor cell is isolated from tumor tissue obtained by biopsy or the like in a conventional manner prior to a treatment and then treated with a drug, and whether this tumor cell is susceptible to the drug is determined based on change of the aforementioned surrogate marker, it becomes possible to preliminarily predict whether the treatment using the drug is effective or not, and this would be extremely useful in clinical practice. It is important that the change of this surrogate marker should be specific to antitumor effect, and it is sufficient that the change can be measured with high sensitivity. Specifically, quantification of variations in the gene expression specific to the antitumor effect of the drug, analysis of quantitative variations of a protein along with the changes in gene expression, analysis of functional changes associated with these changes and so forth can be used as the surrogate markers.
E7070 (N-(3-chloro-7-indolyl)-1,4-benzenedisulfonamide) is a compound that has an antitumor effect targeting the G1 phase of the cell cycle, and is being clinically developed (Takashi Owa, Hiroshi Yoshino, Tatsuo Okauchi, Kentaro Yoshimatsu, Yoichi Ozawa, Naoko Hata Sugi, Takeshi Nagasu, Nozomu Koyanagi and Kyosuke Kitoh, J. Med. Chem, 1999, 42, 3789-3799).
Spectra of intensity of the growth inhibitory action of this compound on various tumor cells are different from those of any of existing anticancer agents, and this compound is expected to have an effect as an anticancer agent having a novel action mechanism. In order to accelerate the clinical development of this drug and early establish a clinical treatment method, and contribute to improvement of QOL of patients by efficiently advancing treatment based on established treatment methods, it is desirable to discover and apply a surrogate marker that can be specifically used upon the administration of the drug.
In recent years, methods of using various DNA microarrays to detect expression levels of a large number of genes at the same time have been established and widely used (Schena M, Shalon D, Davis R W, Brown P O, Science 1995, 270, 467-70; Lockhart, D. J., Dong, H., Byrne, M. C., Follettie, M. T., Gallo, M. V., Chee, M. S., Mittmann, M., Wang C., Kobayashi, M., Horton, H. Brown, E. L., Nature Biotechnology, 1996, 14, 1675-1680).
Also in the field of cancer studies, researches using such DNA microarrays are actively being conducted. For example, in a study in which diffuse large B-cell lymphoma (DLBCL) was investigated by expression analysis using a DNA microarray, DLBCL has been classified into two of different types according to differences in gene expression profiles, and it has been shown that this classification leads to prediction of prognosis (Alizadeh A A, Eisen M B, Davis R E, Ma C, Lossos I S, Rosenwald A, Boldrick J C, Sabet H, Tran T, Yu X, Powell J I, Yang L, Marti G E, Moore T, Hudson J Jr, Lu L, Lewis D B, Tibshirani R, Sherlock G, Chan W C, Greiner T C, Weisenburger D D, Armitage J O, Warnke R, Staudt L M, et al, Nature, 2000, 403, 503-11). Further, there have been a report in which, by analyzing gene expression profiles of a panel of 60 types of cancer cell lines from the National Cancer Institute in the United States, these cell lines were reclassified and their characteristics were examined (Ross D T, Scherf U, Eisen M B, Perou C M, Rees C, Spellman P, Iyer V, Jeffrey S S, Van de Rijn M, Waltham M, Pergamenschikov A, Lee J C, Lashkari D, Shalon D, Myers T G, Weinstein J N, Botstein D, Brown P O, Nat Genet, 2000, 24, 227-35), a report in which relationships of the gene expression profiles of the panel of 60 types of cancer cell lines and susceptibility to various anticancer agents of each cell line were discussed (Scherf U, Ross D T, Waltham M, Smith L H, Lee J K, Tanabe L, Kohn K W, Reinhold W C, Myers T G, Andrews D T, Scudiero D A, Eisen M B, Sausville E A, Pommier Y, Botstein D, Brown P O, Weinstein J N, Nat Genet, 2000, 24, 236-44) and so forth.
Further, there have also been several reports in which changes in gene expression that occurred when anticancer agents were caused to act on tumor cells were examined by similarly using a DNA microarray (partly macroarray using a membrane filter) (Rhee C H, Ruan S, Chen S, Chenchik A, Levin V A, Yung A W, Fuller G N, Zhang W, Oncol Rep, 1999, 6, 393-401. Zimmermann J, Erdmann D, Lalande I, Grossenbacher R, Noorani M, Furst P, Oncogene, 2000, 19, 2913-20. Kudoh K, Ramanna M, Ravatn R, Elkahloun A G, Bittner M L, Meltzer P S, Trent J M, Dalton W S, Chin K V, Cancer Res, 2000, 4161-6). These reports show that the analysis of variations in gene expression is extremely usefFul in comparison of characteristics of two or more cell populations and comprehensive studies of biological changes of cells caused by drug treatment or the like at a molecular level.